The general aim of the project is the study of reactions and interactions of coagulation factors in vitro and in vivo to define further the nature of the blood coagulation mechanism, to determine factors of significance in the pathogenesis of diseases of hemorrhage and thrombosis, and to develop better forms of therapy for these diseases. Platelet function has been studied particularly the effects of agents that cause platelet clumping and aggregation on platelet metabolism directed at determining the significance of factors that stimulate and inhibit enzyme reactions triggered by platelet membrane phenomena. Methods of purifying coagulation factors have been developed and characteristics of the purified factors, particularly anti-hemophiliac factors have been determined. Studies have been done on mechanisms of prothrombin conversion to thrombin and inhibition of conversion by proteolytic enzyme inhibitors. There has been continued study of intravascular coagulation clinically and attempts to develop appropriate sensitive tests for this phenomenon.